Add HTMLPreloadScanner support for <link rel=preload>

third_party/WebKit/Source/core/loader/LinkLoader.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 146 matching lines @@
             document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, DebugMessageLevel, String("Preconnect triggered for ") + href.string()));
             if (crossOrigin != CrossOriginAttributeNotSet) {
                 document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, DebugMessageLevel,
                     String("Preconnect CORS setting is ") + String((crossOrigin == CrossOriginAttributeAnonymous) ? "anonymous" : "use-credentials")));
             }
         }
         networkHintsInterface.preconnectHost(href, crossOrigin);
     }
 }
 
-static Resource::Type getTypeFromAsAttribute(const String& as, Document& document)
+Resource::Type LinkLoader::getTypeFromAsAttribute(const String& as, Document* document)
 {
     if (equalIgnoringCase(as, "image"))
         return Resource::Image;
     if (equalIgnoringCase(as, "script"))
         return Resource::Script;
     if (equalIgnoringCase(as, "style"))
         return Resource::CSSStyleSheet;
     if (equalIgnoringCase(as, "audio") || equalIgnoringCase(as, "video"))
         return Resource::Media;
     if (equalIgnoringCase(as, "font"))
         return Resource::Font;
     if (equalIgnoringCase(as, "track"))
         return Resource::TextTrack;
-    if (!as.isEmpty())
-        document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, WarningMessageLevel, String("<link rel=preload> must have a valid `as` value")));
+    if (document && !as.isEmpty())
+        document->addConsoleMessage(ConsoleMessage::create(OtherMessageSource, WarningMessageLevel, String("<link rel=preload> must have a valid `as` value")));
+    // TODO(yoav): Is this correct? If as is missing or invalid, it should be subject to "connect-src" CSP directives.

[igrigorik, 2016/01/12 22:11:54]

(sorry for late review). To answer the question: yes, I think connect-src is the
right default.. we describe preload s declarative fetch(), so it makes sense to
default to connect-src. 

That said, does LinkSubresource default to this policy?

     return Resource::LinkSubresource;
 }
 
 static void preloadIfNeeded(const LinkRelAttribute& relAttribute, const KURL& href, Document& document, const String& as)
 {
     if (!document.loader())
         return;
 
     if (relAttribute.isLinkPreload()) {
         UseCounter::count(document, UseCounter::LinkRelPreload);
         ASSERT(RuntimeEnabledFeatures::linkPreloadEnabled());
         if (!href.isValid() || href.isEmpty()) {
             document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, WarningMessageLevel, String("<link rel=preload> has an invalid `href` value")));
             return;
         }
-        Resource::Type type = getTypeFromAsAttribute(as, document);
+        Resource::Type type = LinkLoader::getTypeFromAsAttribute(as, &document);
         ResourceRequest resourceRequest(document.completeURL(href));
         ResourceFetcher::determineRequestContext(resourceRequest, type, false);
         FetchRequest linkRequest(resourceRequest, FetchInitiatorTypeNames::link);
 
         linkRequest.setPriority(document.fetcher()->loadPriority(type, linkRequest));
         Settings* settings = document.settings();
         if (settings && settings->logPreload())
             document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, DebugMessageLevel, String("Preload triggered for " + href.host() + href.path())));
         linkRequest.setForPreload(true);
         linkRequest.setAvoidBlockingOnLoad(true);
@@ skipping 82 matching lines @@
         m_prerender.clear();
     }
 }
 
 DEFINE_TRACE(LinkLoader)
 {
     visitor->trace(m_prerender);
 }
 
 }